The mitochondrial nad2 gene as a novel marker locus for phylogenetic analysis of early land plants: A comparative analysis in mosses

The mitochondrial nad2 gene is established as a novel marker locus for phyl ogenetic analyses among early land plants. The potential of this gene for p hylogenetic resolution was checked with a broad taxon sampling of 42 mosses (Bryopsida, including the enigmatic genus Takakia) to allow both a compara tive analysis with the recently explored nad5 gene and the fusion of indepe ndent data sets. The mitochondrial gene sequences provide valuable phylogen etic information on the relationships of classically defined orders and the ir respective monophylies. The more rapidly diverging sequences of a group I intron in nad5 and of a group II intron in nad2 add information for fine resolution. Although both genes provide phylogenetic information in the sam e taxonomic range (above family level), the combined sequence alignment res ults in an approximate doubling in the number of nodes with significant boo tstrap support (>90). According to our data, Buxbaumiales are a paraphyleti c taxon in a key position between the earliest branching taxa (Sphagnales, Takakiales, Andreaeales, Polytrichales, and Tetraphidales) and all other or ders, possibly to be placed in the subclass Bryidae. A dichotomy in the lat ter recalls two previously suggested superorders Hypnanae and Dicrananae. B oth genes independently question the monophyly of the orders Dicranales and Neckerales and reject the inclusion of the genera Schistostega, Timmia, an d Encalypta among Eubryales, (C) 2000 Academic Press.